When microelectronic components are employed in medical implant devices, an important consideration is to protect the microelectronic components from the adverse affects of the aqueous environment usually encountered within the human or animal body. In particular, the moisture or fluids of the human or animal body to which such medical implant devices are almost invariably exposed are typically electrolytic conductors and create a potentially corrosive environment for the microelectronic components, especially when those components are supplied with a direct current (DC) voltage via a battery power source or a converted alternating current (AC) power supply. When the microelectronic components are exposed to corrosive influences, the efficacy of the medical implant device can be compromised leading to reduced performance or even to a complete failure of the device. For example, when an optical receiver element is used in an environment where it is exposed to aqueous solutions or other liquids, proper functioning of the receiver element may be impaired by electrochemical corrosion.
A typical solution to this problem is to enclose or encase the microelectronics and other sensitive components in such a way that they are impervious to moisture. For example, the sensitive components or even the entire medical implant device may be hermetically sealed from the aqueous environment of the body, for example, by an enclosure or a coating layer, such as a polymer coating. Silicone polymers are particularly favorable in this context because of their high bio-compatibility. Such a coating layer, however, not only complicates the manufacturing process, but also has the problem that the microelectronic components still need to maintain an electrical contact with external components. This often requires that a physical connection be provided through the protective enclosure or coating layer and, thus, a breach in the protective enclosure or layer is created. Additionally, while sealing some components or the entire implant device with, for example, a polymer coating layer can provide effective protection from a corrosive environment, it can also involve a conflict between the requirements of impermeability to moisture on the one hand, and flexibility of the implant device on the other, particularly in the field of retinal implants.